A particular suited media for recording optical holograms are amorphous molecular semiconductor films. In this invention it is preferred to employ an AMS-film deposited on a glass substrate pre-covered with a conducting sub-layer, where the AMS-film consists of 92 wt % of a copolymer comprising N-epoxypropylcarbazole and 5 wt % buthylglycedil ether, doped with 5 wt % of methyl-9-(4-dodecyl-oxyphenyl-1,3-selenathiol-2-ylidene)-2,5,7-trinitrofluorene-4-carboxylate (MDOSTFC) and 4 wt % of hexadecyl-2,7-dinitro-dicyanomethylenfluorene-4-carboxylate (H-DDFC). The composition and functioning of this and similar AMS-films are thoroughly discussed and explained in the applicant's Norwegian application no. 19995273, and is incorporated herein by reference.
Optical holographic interferometry technique is well suited for non-destructive testing of internal defects in blocks and units of machines and devices, welded seams, as well as measuring stresses of an object during the object's work load and residual stresses caused by technological processes of welding, forging, soldering etc. These applications are useful for fields such as offshore oil industry, shipping industry, process industry, air industry, and all types of constructions where strength is vital or fatigue may cause a problem.
The principle of optical holographic interferometry can very briefly be described as follows: First a hologram of the investigation area of the object is registered and developed by means of the registering medium. Then the investigation area of the object is subject to a load and slightly deformed. Finally, the investigation area of the object and the registering medium containing the first developed holographic are simultaneously illuminated by the object and reference beam respectively. This results in two simultaneous light waves behind the registering medium, one corresponds to the light wave scattered by the investigation area before loading and the other to the light wave scattered by the investigation area after being exposed to the load. An interferogram of the investigation area is created as a result of the superimposition of these two light waves, and eventual defects in the object are revealed by anomalies in the interference fringe pattern. The principle of the holographic interferometry technique and equipment needed to perform this technique in order to reveal defects and measure internal stresses are given in the applicant's Norwegian applications nos. 19995311 and 19995312. Both applications are incorporated herein by reference.
As mentioned, this invention relates to a method and a control device for performing registration of holograms on an AMS-flim.